docs: def on_for(self, node):    # ('target', 'iter', 'body', 'orelse')
          """For blocks."""
          for val in self.run(node.iter):
              self.node_assign(node.target, val)
              self._interrupt = None
              for tnode in node.body:
                  self.run(tnode)
                  if self._interrupt is not None:
                      break
              if isinstance(self._interrupt, ast.Break):
                  break
          else:
              for tnode in node.orelse:
                  self.run(tnode)
          self._interrupt = None